Rheostat



July 13, 1943. w. G. GREMES RHEOSTAT gwucm bo'v MFFEN G Gemzs.

Filed June 19, 1941 Patented July 13, 1943 UNITED sm'ras FATENT OFFICE RHEOSTAT Warren G. Grimes, Urbana, Ohio Application June 19, 1941, Serial No. 398,838

Claims.

This invention relates to a rheostat and has for an object to provide an improved rheostat especially intended for use in connection with a fluorescent lamp bulb. The fluorescent lamp bulb for which this rheostat is intended is of a type that is provided with a heating filament that must be temporarily used in order to initiate the flow of the current therethrough, but which heating filament should be thrown out of the circuit once the current has started to flow through the filament which causes the fluorescence.

This lamp is therefore provided with three contacts; the first and second contacts lead to the heating filament which is connected across them; the third contact leads to the electrode loop feeding the fluorescent current which returns by way of the second contact.

This type of lamp needs a certain amount of fixed resistance and it is an object of this invention to provide a rheostat especially intended for use in cooperation with this lamp, having the current come through a certain fixed resistance element from whence the current may be directed to both contacts until the operation is initiated, and it is therefore directed solely to the fluorescent electrode. In addition, there is provided a second electrical resistance element so that the amount of current reaching the fluorescent electrode may be varied as desired,

A further object of this invention is to provide a rheostat having a switch for suitably connecting and disconnecting the above-mentioned resistance elements to the lamp anodes in such a way that when the operator wishes to put the fluorescent lamp into operation, he may by manually manipulating the rheostat direct the current through the fixed resistance element to two contacts, and by releasing the rheostat once the fluorescent light has commenced, the heating filament contact is automatically thrown out of the circuit and the fluorescent electrode is left in operation at full power. Thereafter, if he so desires, the operator may manipulate the rheostat to cut in a variable amount of the resistance element to cut down the power to the fluorescent electrode.

A further object of this invention is to provide a rheostat manually controllable by rotation of a knob, wherein the knob may be manually held in a certain position to simultaneously connect two conductors therefrom and which knob, when manually released, will automatically disconnect one of the conductors from the circuit and leave only one of the other conductors in the circuit.

With the foregoing and other objects in view, as

will hereinafter become apparent, this invention comprises the combinations, constructions and arrangements of parts hereinafter set forth, disclosed, claimed and illustrated in the accompanying drawing.

In the drawing,

Fig. 1 is an elevational view showing the lamp and the rheostat conveniently mounted in juxtaposition;

Fig. 2 is a rear view of Fig. 1 showing the brush in the position where it is manually held for directing current to two lamp contacts;

Fig. 2a is a fragmentary View showing the brush directing the current to onl one of the contacts after the control knob has been manually released;

Fig. 3 is a schematic view showing the path of the circuits through the rheostat; and

Fig. 4 is a sectional view on line 4-4 of Fig. 1.

In order to better understand this invention, there is shown at H] a lamp bulb which, while being no part of this invention per se, best illustrates the use to which the rheostat of this invention is to be put. This lamp bulb I0 is of the type for emitting fluorescent light which is rich in ultra violet light. As is known, fluorescent lamps in general cannot be caused to start in operation merely by placing normal operating voltage across their terminals. The gases in a fluorescent lamp through which the current must flow in order to operate the lamp must be heated to a certain temperature to render. them most conductive to electricity. Once they are heated to the proper temperature, they will be maintained at 1 such temperature by the flow of the current therethrough so long as such current is uninterrupted.

Accordingly, this lamp ll] includes a gas heating filament ll connecting the contact [2 to the ground 13. A second contact I4 conducts the current to a loop or fluorescent electrode 15 from where, once the gases have been properly heated, the current will pass through the gases, maintaining them at the proper temperature, causing the light to be emitted from the lamp, and the current, after passing through the gases, goes to the wire E6 of the heating filament I l and thence to the ground I3.

Now discussing the rheostat ll of this invention, it will be observed from the schematic showing in Fig. 3 that the current coming in from t conductor [8 from any suitable source of power passes through a fixed resistance element 29. At

the end of this resistance element 23 there is a conductor 2| leading to a conductor terminal 22, this conductor terminal 22 being spaced from the end of the fixed resistance element 20. Occupying this space between the end of the fixed resistance element and the conductor terminal 22 is a similar conductor terminal 23 adjacent the conductor terminal 22 and then an insulated stop member 24 extending somewhat above the top of the conductor terminals 22 and 23. The conductor terminal 22 has connected to it a second electrical resistance element 25, at the end of which is located a boss 26 providing a position indicating means extending slightly above the top of the surface of the variable resistance element 25. The conductor terminal 23 is connected by a conductor 27 to the heating filament contact l2. A rheostat brush 28 is connected by a conductor 38 to the fluorescent contact Hi. This rheostat brush 28 is of such width that when suitably positioned it will bridge the conductor terminals 22 and 23, as shown in Fig. 3.

This rheostat brush 28 is mounted on the end of the rheostat arm 3 I, the conductor 3!] connecting to the brush 28 through the arm 3|, as brought out in Figs. 2 and 2a. This arm 3! is mounted on a rotatable shaft 32 which extends through the rheostat and is provided with a manually manipulatable control knob 33. Also secured to this rheostat arm 3! is a leaf spring 33. This leaf spring 34 extends out to one side of the rheostat arm 3|, and when the rheostat arm 3! is rotated over the electrical resistance element toward the conductor terminal 22, the end of the leaf spring 33 comes into contact with the insulated stop 24 simultaneously with the brush 28 coming into contact with the conductor terminal 22. In order that the brush 28 may pass sufficiently beyond the conductor terminal 22 so that it bridges the conductor terminal 22 to the conductor pole 23, as shown in Fig. 3, the leaf spring 33 must be flexed by manually rotating the knob 33 somewhat forcibly until the leaf spring 32 assumes the position shown in Fig. 2, permitting the brush 28 to bridge both conductor terminals 22 and 23.

' While held in this position, the current flows from the conductor l8 through the fixed resistance element 20 and through the conductor 2i, passes to the conductor terminal 22 and through brush 28 to both the conductor 38 leading to fiuprescent contact l4 and the conductor terminal 223 and conductor 2! leading to the heating element contacts l2 and Id. The current will flow to both anodes so long as the knob 33 is manually held in this position. Once the knob 33 is released, however, the spring 34 resumes the position shown in Fig, 2a, slightly rotating the rheostat arm 3! and causing the brush 28 to remove itself from the bridging position over conductor terminals 22 and 23, shown in Figs. 2 and 3, hack to the position shown in Fig. 2a, where the brush 28 is in contact only with conductor teranimal 22.

If the operator desires to cut down the amount cf current reaching the fluorescent electrode l5, he merely rotates the knob 33 causing the brush 28 to leave the conductor. terminal 22 and pass over the second resistance element 25. The spring 34 will in no way interfere with this movement because it is not secured to the insulated stop 26. It is secured only to the rheostat arm 3| and is so positioned that it abuts against the insulated stop 26 only when the rheostat arm is about to move the brush 28 from solely over conductor pole 22 to the bridging position over both conductor terminals 22 and 23. It is therefore free to move away therefrom and when so moved awai it is completely out of contact with any other element and performs no function. As the rheostat arm 3i approaches the off position 35 at the end of the rheostat the brush 28 first contacts the boss 26 thereby providing a slight physical resistance to the further rotation of the arm 3! and of the manual knob 33. This slight physical resistance acts as a position indicating means to inform the operator that he has reached the end of the second resistance element 25 and that further movement will cause the brush 28 to move to the off position at 35 and disconnect his lamp Ill. Once this has happened the lamp can be placed in operation again only by rotating the knob 33 back again until the brush 28 has passed beyond the second resistance element 25 to the bridging position over both conductor terminals 22 and 23 and held in that position until the current through the heating filament H has sufficiently heated the gas to allow the current to pass through the fluorescent gases therein, whereupon, by releasing the knob 33, the spring 34 will slightly rotate the rheostat arm 3| to disconnect the current to the conductor terminal 33 and thus to the heating element ll.

While the device has been shown and the structure has been described in detail, it is obvious that this invention is not to be considered limited to the exact form disclosed and that changes may be made therein within the scope of what is claimed Without departing from the spirit of the invention.

Having thus set forth and disclosed the nature of this invention, what is claimed is:

l. A rheostat comprising a fixed electrical resistance element, a conductor means connected to said fixed resistance element, a second conductor means spaced from said first conductor means, a rheostat brush, means for forcibly moving said rheostat brush to a position bridging both conductor means, means yieldably resisting the movement of the rheostat brush to the bridging position in contact with both conductors and restoring said brush to a position in contact with the first-mentioned conductor when the force is released, a conductor connected to said brush, and a second conductor connected to said second conductor means whereby when said brush is forcibly held in bridging position in contact with both conductor means current may flow through both conductors and, when the force holding the brush is released, current will flow only through the conductor connected to said brush, a second electrical resistance element connected to said first conductor means, said brush being movable over said second electrical resistance element to decrease the current passing through the conductor connected thereto.

2. A rheostat comprising a fixed electrical resistance element, a conductor means connected to said fixed resistance element, a second conductor means spaced from said first conductor means, a rheostat brush, means for forcibly moving said rheostat brush to a position bridging both conductor means, means yieldably resisting the movement of the rheostat brush to the bridging position in contact with both conductors and restoring said brush to a position in contact with the first-mentioned conductor when the force is released, a conductor connected to said brush, a second conductor connected to said second conductor means whereby when said brush is forcibly held in bridging position in contact with both conductor means current may flow through both conductors and, when the force holding the brush is released, current will flow only through the conductor connected to said brush, a second electrical resistance element connected to said first conductor means, said brush being movable over said second electrical resistance element to decrease the current passing through the conductor connected thereto, a position indicating means at the end of said second electrical resistance means, and an off position for such brush beyond said position indicating means whereby said position indicating means signals the operator that the brush is about to leave the second electrical resistance element to the off position.

3. A rheostat comprising a fixed resistance element, a conductor means connected to said fixed resistance element, a second conductor means spaced from said first conductor means, a rheostat brush, means for forcibly moving said rheostat brush to a position bridging both conductor means, and means yieldably resisting the movement of the rheostat brush to the bridging position in contact with both conductors and restoring said brush to a position in contact with the first-mentioned conductor when the force is released, said yieldably resisting means comprising a spring mounted in the path of movement of the brush when the brush is being moved from contact with the first conductor means to the bridging position in contact with both conductor means, said spring forcibly yielding as the brush is forcibly moved to the bridging position and returning to unflexed position when the force is released to remove the brush from the bridging position and restore it to the position in contact with the first-mentioned conductor.

4. A rheostat comprising a fixed resistance element, a conductor means connected to said fixed resistance element, a second conductor means spaced from said first conductor means, a rheostat brush, means for forcibly moving said rheostat brush to a position bridging both conductor means, and means yieldably resisting the movement of the'rheostat brush to the bridging position in contact with both conductors and restoring said brush to a position in contact with the first-mentioned conductor when the force is released, said yieldably resisting means comprising a spring mounted in the path of movement of the brush when the brush is being moved from contact with the first conductor means to the bridging position in contact with both conductor means, said spring forcibly yielding as the brush is forcibly moved to the bridging position and returning to unfiexed position when the force is released to remove the brush from the bridging position and restore it to the position in contact with the first mentioned conductor, said spring comprising a leaf spring, one end of said spring being mounted on a common mounting means with said movable brush, and a suitably located stop means adapted to be abutted by the other end of said leaf spring when said brush is being forcibly moved to the bridging position.

5. A rheostat comprising a fixed electrical resistance element, a conductor means connected to said fixed resistance element, a second conductor means spaced from said first conductor means, a rheostat brush, means for forcibly moving said rheostat brush to a position bridging both conductor means, means yieldably resisting the movement of the rheostat brush to the bridging position in contact with both conductors and restoring said brush to a position in contact with the first-mentioned conductor when the force is released, a conductor connected to said brush, a second conductor connected to said second conductor means whereby when said brush is forcibly held in bridging position in contact with both conductor means current may flow through both conductors and, when the force holding the brush is released, current will flow only through the conductor connected to said brush, a second electrical resistance element connected to said first conductor means, said brush being movable over said variable element to decrease the current passing through the conductor connected thereto, a position indicating means at the end of said second electrical resistance means, and an off position for such brush beyond said position indicating means whereby said position indicating means signals the operator that the brush is about to leave the second electrical resistance element to the off position, said yieldably resisting means comprising a spring mounted in the path of movement of the brush when the brush is being moved from contact with the first conductor means to the bridging position in contact with both conductor means, said spring forcibly yielding as the brush is forcibly moved to the bridging position and returning to unflexed position when the force is released to remove the brush from the bridging position, said spring comprising a leaf spring, one end of said spring being mounted on a common mounting means with said movable brush, and a suitably located stop means adapted to be abutted by the other end of said leaf spring when said brush is being forcibly moved to the bridging position.

WARREN G. GRIMES. 

